A New Troodontid Dinosaur (Liaoningvenator currieigen. et sp. nov.) from the Early Cretaceous Yixian Formation in Western Liaoning Province

A new troodontid,Liaoningvenator curriei gen. et sp. nov., is described based on a complete skeleton from the Early Cretaceous Yixian Formation of Beipiao City, Liaoning Province. It bears the following characteristics of Troodontidae: numerous and more closely appressed maxillary and dentary teeth; the teeth markedly constricted between the roots and crowns; the nutrient foramina in groove on the external surface of dentary; distal caudal vertebrae having a sulcus on the dorsal midline rather than a neural spine. Unlike other troodontids, Liaoningvenatorexhibits a sub-triangular ischial boot in lateral view and slender ischial obturator process; transition point in caudal vertebrae starts from the seventh caudal vertebra. A phylogenetic analysis recovers LiaoningvenatorandEosinopteryx as sister taxa that belong to the same clade. These two taxa share the following three characteristics: (1) anterior maxillary and dentary teeth lack serrations along the anterior carina; (2) shafts of cervical ribs are longer than vertebral centra with which they articulate; and (3) anterior margin of ilium is straight. The histological study indicates that Liaoningvenator was attaining skeletal maturity and at least four years old when it perished.Liaoningvenator represents the fifth troodontid taxon from the Lower Cretaceous equivalent strata of western Liaoning. It provides much new anatomical information on basal troodontid dinosaurs in this region. It also enhances the diversity of the troodontids in Early Cretaceous of China currently known.